Implant Thread Design: Influence on Osseointegration?

Threads are used to maximize initial contact, improve initial stability, enlarge implant surface area, and improve the dissipation of stresses at the interface. Thread depth, thread thickness, thread face angle, thread pitch, and thread helix angle are some of the geometric variations that determine the functional thread surface and affect the biomechanical load distribution around the implant. The threads are as influential that as the greater the numbers of threads that are present as well as the greater the depth of the threads, we will have more functional surface area. The face angle of the thread can change the direction of load from the prosthetic load to a different force direction at the bony contact area. Therefore, design considerations that reduce the development of shear at the dental implant–tissue interfaces might improve long-term success, especially in low-density bone (D4) areas. Clones of implants have been presented to market as “double-threaded” or “triple-threaded”. While the implant may be fully seated in half the time, because of the tapered shape of the implant apex, higher apical torque bone compression occurs during the last revolution of placement, increasing implant rigidity and stability. More innovations in implant designing have lead to introducing a rounded thread design that claims to induce “osteocompression.” Through biomechanical events in bone, osseous tissue can be stimulated within physiological limits by implant design to develop along the lines of compressive forces dependent on the implant load-bearing area to sustain equilibrium. Studies have shown that threaded implants have higher remodeling rates and less mineralized bone formation when loaded with axial force than the non-loaded threaded implants. Increasing remodeling activity in bone which is observed near loaded implants supports Frost’s theory in mechanical engineering that these responses are triggered by tissue micro-damage as a direct result of the loading. In the recent years, some implant manufacturing companies have presented their products with microthreads on their collar neck. It's been shown that these microthreads potentially decrease the amount of crestal bone loss; however, the effect of the microthread on the early stabilization of the crestal bone level has not been verified. According to the study on the mechanical property of the bone (Guo 2001), bone is most resistant against the compressive strength and 30% less against the tensile strength and65% less resistant against the shear strength. Therefore, to minimize the bone loss, the crestal module design, which can decrease the shearing stress on the crestal bone, is important. Further research on the microthread and other fixture designs would be necessary in the future.

xxcellent post.like the thread design what are the studies and literature supporting surface coating or surface treatments of implants.will it have a role in primary stability

which implant system/systems has the ideal thread which you recommend and practise

"Are you talking to me?" (Robert DeNiro in Martin Scorsesse's Taxi Driver).

Hi ! The bone is absolutely doof ! The bone doesn't recognize designs only materials. The design of the threads is important only for primary stability and therefore for early loading. After integration there is no difference in behavior of implants with different thread forms.

The thread design IS important beyond primary stability. The lecture of the following paper is of great interest in supporting my point : Hansson S and Werke M. The implant thread as a retention element in cortical bone: the effect of thread size and thread profile: a finite element study. J Biomech. 2003 Sep;36(9):1247-58.

There are many studies on thread design and how they relate to Wolff's law. It indeed does have some effect but is simply one variable in the equation of bone resorption, integration, stability and preservation of the coronal bone margin. Osteocompression isn't always a good thing. Back in 80's to repair fractures we used dynamic eccentric compression plates. As you torques the screws into the bone, the eccentric screw hole would cause the the bone plate to compress the bone at the fracture site. It was felt that compression aided in bone healing. Well, those plates aren't used much as the compression caused resorption and there were more fibrous unions and non-unions. Over-compression is not a good thing. Now fractures are approximated and held static and that yields the best result. Healing of implants is extremely similar to the stages of healing of fractures. The same rules apply. You need immobility or relative immobility to have integration and wolff law does apply to both implants and fractures.

we have seen threads to the neck -no threads at neck- one mm smmoooth neck; some with more smmoth neck.many of us have placed "cylinder" implants with no threads that work -integrate. So whats best how do we prevent bone loss at neck "to the first Thread" ?